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A new theory of life

Melissa Beattie-Moss

January 29, 2007

A new theory of life

Beneath the kelp beds off the coast of southern California, in an oxygen-free and carbon-monoxide rich environment, an obscure undersea microbe called Methanosarcina acetivorans is thriving, due to its unique metabolism.

Courtesy Everly Conway de Macario and Alberto J. L. Macario.

Live culture of Methanosarcina acetivorans cells.

While other microbes make methane from carbon monoxide, researchers have shown that this species also produces acetate—commonly known as vinegar—in a unique metabolic process that may shed new light on the evolution of life and lay the foundation for a new source of clean fuel.

"The bug," as microbiologist J. Greg Ferry calls the microbe, "is very ancient indeed. It is quite possible that it represents the first metabolic cycle on the planet."

Ferry, Penn State's Stanley Person professor of biochemistry and molecular biology, discovered and named M. acetivorans 20 years ago and has been immersed in the field of anaerobic microbes since then. In the June 2006 issue of Molecular Biology and Evolution, he and assistant professor of geosciences Christopher House published results of a study that not only unlocks the biochemistry of how M. acetivorans produces acetate but also
inspired them to construct a fundamental new theory of the origin of life on Earth.

This new, "thermodynamic" theory of evolution proposes a central role for energy conservation during early evolution, based on a simple three-step biochemical mechanism. "It reshapes the two previous theories of life's origin, it shows how they overlap, and it extends both of them significantly," Ferry says.

The road to this discovery was paved in 2001 when Ferry and others urged colleagues at MIT's Whitehead Institute to sequence the microbe's genetic code. Less than a year later, they handed him the results of the sequencing. "For the first time we were seeing the details of how the bug works," said Ferry. "It was almost overwhelming, actually."

Anaerobes comprise nearly one-fourth of all living protoplasm on earth and the methane by-product of their metabolism may represent a renewable, clean-burning energy source. The Department of Energy and the NASA Astrobiology Institute both have sponsored Ferry's research.

"Methanosarcina and other anaerobes are our ancestors," reminds Ferry. "They laid down the metabolism for life as we know it today."